The present invention relates to winders for safety belts and more particularly to a winder for a safety belt which has a tightener employing a spring and is automatically locked under the control of an inertia unit.
As is known, as required by the public authorities, ground automobile vehicles are mass-produced already equipped with safety belts.
For the comfort of the passengers, these safety belts are provided with a winder which includes a spring-biased tightener and is automatically locked under the control of an inertia unit. In this way, the strap of the safety belt, which is usually held taut and applied against the passenger, is provided with a certain possibility of mobility if the movements to which it is subjected are not too sudden. Otherwise, in the case of sudden movements acting on the strap, the latter is automatically locked or blocked under the action of an inertia unit which is responsive both to the horizontal component of the deceleration of the vehicle and to the tangential component of the acceleration of the unwinding of the strap in opposition to the force exerted by the return spring of the tightener. When the strap is thus immobilized, the stresses to which it is subjected by the forces exerted thereon by the passenger are transmitted to the structure of the vehicle.
It will therefore be understood that, in the event of a sudden deceleration of the vehicle which may be as much as several "g", the winder of the safety belt is subjected to particularly severe stresses which it must resist if it is not to lose its effectiveness. This is why the immobilization of the hub on which the strap of the safety belt is wound is effected in two stages. Whether it is upon the detection of a tangential or horizontal component of acceleration which exceeds a predetermined value, the hub is first of all immobilized in rotation and then finally locked by means which are capable of withstanding considerable forces.
In order to obtain such an automatic locking which occurs as just recalled, the hub on which and from which the strap of the safety belt is wound, is movable both in rotation about its axis and in translation in a direction perpendicular to its axis of rotation.
Various arrangements have already been proposed to obtain these two degrees of freedom.
According to a method proposed by the French patent 2 367 508, the bearing in which the hub is movable are relatively free and are movable without guiding in an opening which has a substantially "delta" triangular configuration formed in the parallel walls of a U-shaped base.
According to another arrangement disclosed by the European patent 0 112 033, these bearings are movable in translation in slots provided in end plates which are so mounted as to be pivotable on the parallel walls of a U-shaped base.
Neither of these arrangements is fully satisfactory.
Indeed, the first arrangement is such that the bearings are not effectively guided since they are free to move in openings having dimensions exceeding the dimensions of the bearings. The axis of the hub may be inclined and become askew.
The second of these arrangements is prohibitive since it is complicated and employs many components which are expensive to manufacture and assemble.